Toxicity Tests : Experimental details

The river water being investigated has been polluted by effluents from the Chemical industry at Northwich which contain high levels of dissolved salts which make the River Weaver 'brackish'. The proportions of these salts alter in time but their differential contribution may be important in determining the toxicity of the effluent to freshwater invertebrates.

'Toxins' included in investigation:

• Common Salt - Sodium Chloride - NaCl
• Calcium Chloride - CaCl₂
• Ammonium Chloride - NH₄Cl

Solutions should be made up at logarithmic intervals of concentration. No solutions need to be more concentrated than 100 mg l^-1

Experimental Containers

100 ml Beakers or jars (you are provided with a maximum number of N - (N will be given in the class)

Sediments

1. Sediments were collected from above Northwich
2. Below Winnington Park, Northwich
3. The Weston Canal, which runs into the Weaver near Runcorn

Experimental animals

You are provided with a maximum of 25 animals per group from each of the two species (No of Animals may vary - details given in the class)